A liquid crystal display (LCD) includes a liquid crystal alignment layer. The liquid crystal alignment layer is mainly made of polymer materials. The liquid crystal photo-alignment layer plays a role of a director in aligning liquid crystal molecules. When the liquid crystal molecules are moved by the influence of an electric field to display an image, the liquid crystal photo-alignment layer allows them to be oriented in a predetermined direction. Generally, it is necessary to uniformly align the liquid crystal molecules in order to provide uniform brightness and a high contrast ratio to the liquid crystal device.
The conventional method of aligning the liquid crystal includes coating a polymer membrane such as a polyimide on a substrate made of a material such as glass, and rubbing the surface of the substrate with a fiber such as nylon or polyester in a certain direction. However, the rubbing method may cause serious problems while fabricating a liquid crystal panel due to fine dust or electrostatic discharge (ESD) that may be generated while rubbing the polymer membrane with the fiber.
In order to solve the problems of the rubbing method, there has been recent research on a photo-radiation method of inducing anisotropy to a polymer membrane by irradiating light on the membrane and thereby aligning liquid crystal molecules thereon. The photo-alignment method uses a polymer membrane material such as polyamic acid, a polyimide, or a polymer thereof, which is derived from diamines having a photo-functional group such as azobenzene, cumarine, chalcone, and cinnamate. The polymer material is dissolved in an organic solvent to prepare a liquid crystal photo-alignment agent. When the liquid crystal photo-alignment agent has poor printing properties, it may deteriorate photo-alignment properties, for example the vertical alignment property, during the operation of a liquid crystal display. Accordingly, there is active research on a liquid crystal photo-alignment agent having excellent printing properties, vertical photo-alignment properties, and the like.